The field of the invention relates to microsurgery, and particularly to microsurgery which involves the making of an incision and the use of heat-generating equipment which is inserted through the incision.
Microsurgical systems are used for performing many operations today, including ophthalmic surgery. Systems for removing cataracts, for example, typically include a cutting probe and associated aspiration device for removing macerated tissue to a collection vessel. An irrigation supply is also provided to replace the fluid removed through aspiration.
Devices for performing ocular microsurgery through the use of an ultrasonic generator and vibrating tool have seen widespread use. One such device is described in U.S. Pat. No. 3,589,363. The patented device includes a hand piece including an ultrasonic vibrating tool. Such a tool is used to break up unwanted tissue, such as cataractous tissue, which is then removed via irrigation and aspiration procedures. The tool is inserted through a small incision made in the eye to gain access to the defective lens tissue. The tool extends through the incision during the entire operation as the surgeon breaks up the tissue with the tool and causes its removal. Upon completion of the operation, an artificial lens is implanted in place of the cataractous lens, and the incision is stitched closed. The above procedure is generally known as phacoemulsification.
A number of different types of ultrasonic cutting tools are known to the art. U.S. Pat. Nos. 4,417,578, 4,643,717 and 4,681,561 disclose three such tools. Such tools operate at frequencies above twenty thousand Hz.
The advantage of cataract removal via phacoemulsification is the relatively small wound (incision) necessary to gain access to the cataract. The ultrasonic instrument used to emulsify the cataract generates heat, however, which causes the collagen around the wound to shrink. This tends to open the wound rather than allowing it to remain as a slit. If the wound is closed tightly, the cornea will be distorted, causing astigmatism. If the wound is not closed tightly, it will tend to leak. In addition, the iris may not stay in place if the wound is not tightly closed.
There is accordingly a need for a method which allows full advantage to be taken of the small incisions made in surgical procedures such as phacoemulsification.